A variety of designs have been utilized for local area network (LAN) communication systems. One local area network communication system is depicted in FIG. 1. The system depicted in FIG. 1 may be termed a bus based Ethernet LAN broadcast system. User stations 13, 15, 17 and 19 are each connected to bus 11. When, for example, user 13 wishes to communicate, he transmits information to bus 11. The information is potentially available to users 15, 17 and 19. The user having the correct destination address receives and interprets the information. (If the system is equipped with a security feature, other users who have different destination addresses presumably cannot access the information.)
Another popular system is depicted in FIG. 2. Reference numeral 21 denotes a multiple port repeater based Ethernet LAN. The configuration depicted in FIG. 2 is often termed a "star topology." Users 23, 25, 27, 29, 31 and 33 are each connected to a single, multiport repeater 21. Should user 23, for example, wish to transmit information, the information is transmitted to repeater 21. Repeater 21 rectifies various forms of signal degradation which may have occurred during transmission and then broadcasts the information to users 25, 27, 29, 31 and 33. The user having the correct destination address receives and interprets the information, while users with different destination addresses either: (i) receive the information anyway, or (ii) cannot receive the information because a security feature prevents them from receiving it due to their incorrect destination addresses.
Both of the systems depicted in FIGS. 1 and 2 have several shortcomings. Each system is a collision-based system. Thus, when one user, for example, user 23 or user 13, is transmitting information, other users cannot transmit. Should another user attempt to transmit, a collision results and the other user's transmitter backs off and waits for another opportunity to transmit. Thus, only a single user may transmit at any given time period.
In both the systems depicted in FIG. 1 and FIG. 2, a single medium, either bus 11 or multiport repeater 21 is shared by all users.
Each of the systems in FIG. 1 and FIG. 2 is theoretically capable of handling a large number of users, for example, as many as 1,024 users. However, because of the collision problem, as the number of users increases, the effective bandwidth per user decreases. In other words, as the number of users increases, the efficiency of the system in transmitting information decreases.